Repellent system for lithographic duplicators



March 22, 1960 w, ow 2,929,316

REPELLENT SYSTEM FOR LITHOGRAPHIC DUPLICATORS Filed April 26, 1956 2Sheets-Sheet 1 I76 F26 .L 2 v A 43 as I! x- INVENTOR. Mllace E.fburlz'c.

BY 1pm March 22, 1960 w. R. FOWLIE REPELLENT SYSTEM FOR LITHOGRAPHICDUPLICATORS 2 Sheets-Sheet 2 Filed April 26, 1956 INVENTOR. 1 WallaceB.F0wlzc United States Patent REPELLENT SYSTEM FOR LITHOGRAPHICDUPLICATORS Wallace R. Fowlie, North Riverside, Ill., assignor to A. B.Dick Company, a corporation of Illinois Application April 26, 1956,Serial No. 580,788

10 Claims. (Cl. 101-148) This invention relates to lithographicduplicators or printing machines and particularly to repellent systemsfor applying water or other liquid ink repellent to lithographic masterplates or sheets employed on such machines.

One principal object of the present invention is to provide a new andimproved repellent system for a lithographic printing machine, wherebythe amount of repellent applied to the lithographic master may becontrolled and varied as desired, in a convenient and advantageousmanner.

A further object is to provide a new and improved repellent system whichaffords an extremely wide range of adjustment of the rate at whichrepellent is applied to the master.

Another object is to provide a new and improved repellent system havingadjusting means which may readily be operated with the printing machinerunning.

It is a further object to provide a repellent system having new andimproved means for completely suspending the feeding of repellent.

Further objects and advantages of the present invention will appear fromthe following description, taken with the accompanying drawings, inwhich:

Fig. l is a diagrammatic side elevational View of-an offset-typelithographic duplicator equipped with a repellent system constitutingone illustrative embodiment of the present invention.

Fig. 2 is a fragmentary enlarged side elevational view showing amanually adjustable lever and associated mechanism for adjusting therate at which repellent is fed to the master cylinder, the view beingpartly in section for clarity of illustration.

Fig. 3 is a fragmentary perspective view showing a portion of therepellent system. I

Fig. 4 is a fragmentary enlarged side elevational view of the repellentsystem with certain parts of the machine removed for clarity ofillustration.

Fig. 5 is a view similar to Fig. 4 but with certain components shown insection, the adjustment of the mechanism being such as to providemaximum transfer of repellent to the master cylinder.

Fig. 6 is a view similar to Fig. 5, but with the mechanism adjusted tointerrupt the transfer of repellent.

Fig. 7 is another view similar to Figs. 5 and 6, but with the mechanismadjusted to give an intermediate rate of repellent flow to the mastercylinder.

As already indicated, Fig. 1 illustrates an offset-type lithographicduplicator 10 equipped with a master cylinder 12, an offset or blanketcylinder 14, and an impression cylinder 16. Machines of this type areknown in the art. The master cylinder 12 is adapted to hold alithographic master plate or sheet having an ink receptive imagethereon. The non-image areas of the master are receptive to water orother liquid repellent. When coated with repellent, the non-image areasare not receptive to ink.

The blanket cylinder 14 is engageable with the master cylinder 12 and isadapted to receive an offset, reverse,

2 inked image therefrom. Copy sheets or the like are adapted to be fedbetween the offset and impression cylinders 14 and 16 so that the inkedimage on the offset cylinder 14 will be transferred to the copy sheets.

Ink is applied to the master on the master cylinder 12 in a knownmanner, by means of an inking system 18. In this instance, the ink issupplied by an ink fountain 20 which includes an ink fountain roller 22.An oscillating ductor roller 24 transfers the ink intermittently to atransfer roller 26, which carries the ink to a second transfer roller28. A distributor roller 32 carries the ink between the transfer roller28 and another transfer roller 30. In order to spread the ink evently,the distributor roller 32 may be made to oscillate endwise in a knownmanner. The roller 30 engages a roller 34, which in turn engages twoform rollers 36 and 38. It will be seen that the form rollers 36 and 38actually engage the'master cylinder 12 and are adapted to transfer thekink to the master.

In the illustrated machine, an additional distributor or transfer roller40 engages the form roller 36. The distributor roller 40 may beoscillated in an axial direction to spread the ink, although suchoscillation may be considered optional. In addition, the roller 40serves to carry repellent to the form roller 36 and thence to thelithographic master on the master cylinder 12. Thus the roller 40 andthe form roller 36 are components of both the inking and repellentsystems of the machine. The other form roller 33 and the roller 34 alsoplay a part in distributing and spreading the repellent.

Repellent is supplied to the distributor or transfer roller 40 by meansof a repellent mechanism 42. Most of the components of the repellentmechanism 42 are mounted on a sub-frame 44 Which is detachably mountedon the printing machine 10 so that the repellent system may readily beremoved from the machine. In this instance, the repellent sub-frame 44has forked lugs 46 and 48 adapted to be mounted on studs or the like 50and 52 carried by main side frames or plates 53 and 54 on the machine10.

The repellent or dampening mechanism 42 includes a trough-shapedrepellent fountain 56 which, in this instance,

is formed as a portion of the repellent sub-frame 44. A.

repellent fountain roller 58 is positioned in the fountain 56 so as tobe partly immersed in a pool 60 of repellent contained therein.Repellent is fed to the fountain 56 from a reservoir 62 of the invertedbottle-feeder type. In this way, the level of the repellent ismaintained approximately constant in the fountain 56.

The fountain roller 58 picks up the water or other repellent from thefountain 56 and applies the repellent to a transfer roller 64 whichcontinuously engages the fountain roller 58. Any suitable material maybe employed in the fountain roller 58, such as metal with a roughenedsurface. Likewise, any suitable material may be employed in the transferroller 64, such as rubber, synthetic rubber, or other soft, resilientmaterials. The fountain roller 58 may be continuously driven by suitablegearing or the like, not shown, approximately at the peripheral speed ofthe master cylinder 12 and the various inking rollers. The transferroller 64 may be frictionally driven by the fountain roller 58.

In the illustrated machine, the transfer roller 64 is mounted forrotation about its own axis, and for swinging movement about the axis ofthe fountain roller 58. It will be seen that the transfer roller 64 isswingable into and out of engagement with the distributor roller 40.When the transfer roller 64 engages the roller 40, repellent istransferred thereto and thence is conveyed to the master cylinder 12.

It will be seen that the illustrated transfer roller 64 is rotatablymounted on a shaft 66 carried on a pair of swing frames or carriages 68.To allow movement of the roller 64 toward and away from the roller 58,each carriage 68 is formed with a longitudinal slot 68a. A bearing 69 isslidable in each slot 68a. Each bearing 69 supports one end of theroller shaft 66. Springs 70 are mounted on the carriages 68 to bias thetransfer roller 64 against the fountain roller 58. The springs 70 arebacked up by manually adjustable screws 72 which may be rotated to varythe pressure between the rollers 58 and 64. Such pressure variationaffects the rate at which repellent is fed to the master cylinder 12.

It will be seen that the fountain roller 58 is provided with end shafts74 which support the fountain roller for rotation about its own axis. Inaddition, the carriages 68 are pivoted in coaxial relation to the shafts74 for swinging movement about the axis of the fountain roller.

Provision is made for oscillating the roller 64 and the carriages 68 ina variable manner so as to vary the time intervals during which theroller 64 engages the distributor roller 40. In this instance, thetransfer roller 64 is biased toward the distributor roller 40 by meansof springs 76 which act upon the carriages 68. Cam follower levers 78are provided to swing the transfer roller 64 away from the distributorroller 40, counter to the biasing action of the springs 76. Lost motionconnections are provided between the levers 78 and the carriages 68 sothat the range of movement of the levers may exceed that of thecarriages. More specifically, each of the levers 78 has an upper arm 80which carries a roller 82 adapted to engage a lug 84 on thecorresponding carriage 68.

Oscillating motion is imparted to the cam follower levers 78 by means ofcams 86 which are rotatable about shafts 88. Suitable gearing isemployed to drive the earns 86, preferably at a rotary speed differingslightly from that of the master cylinder 12 and not a multiple orsub-multiple thereof. In this way, the cycle of the cams 86 will differslightly from that of the master cylin- .der so that repellent will besupplied thereto with improved uniformity. More specifically, each ofthe illustrated earns 86 is provided with a gear 90 which meshes with aslightly smaller gear 92 secured to the master cylinder 12. Withthis'manner of driving thercams 86, :quite a number of cycles of themaster cylinder 12 will elapse before there is any repetition of similarrelationships between the master cylinder and the repellent system.

To ride the cams 86, a roller 94, is mounted on a lower arm portion 96of each lever 78. A spring 98 is arranged to bias the lever 78 so thatthe roller or rider 94 will continuously engage the corresponding cam86.

It will be seen that each of the follower levers 78 is -swingablymounted on a pivot 100. Provision is made for shifting the pivots 100laterally so as to vary the -manner in which the roller 64 isoscillated. In this inranged to mesh with a pinion 110 secured to thepivot shaft 102. The range of swinging movement of the lever 104 islimited by a pin 112 which extends through an arcuate slot 114 formed inthe lever.

Rotating the eccentric pivots 100 moves the rollers 82 :toward and awayfrom the lugs 84 on the carriages 68.

ment with the distributor roller 40. Under these conditions, a' maximumamount of repellent will be fed to the master cylinder 12.

In Fig. 6, the pivots have been turned through 180 degrees so as to movethe levers 78 toward the carriages 68 to the maximum possible extent.Under this condition, the carriages 68 will follow the levers 78throughout their range of oscillation, and the transfer roller 64 willbe held away from the distributor roller 40 at all times. In otherwords, there will be no contact between the transfer roller 64 and thedistributor roller 40. Accordingly, no repellent will be fed to thedistributor roller 40.

It will be understood that the pivots 100 may be adjusted to anyintermediate position between the extremes represented by Figs. 5 and 6.Fig. 7 illustrates one intermediate position in which the transferroller 64 will engage the distributor roller 40 intermittently, for apor-' tion of each cycle of the earns 86. By adjusting the posi tion ofthe control lever 104, the time of engagement between the rollers 64 and40 may be varied as desired. In this way, the amount of repellent fed tothe master cylinder may be closely controlled.

Provision is made for moving the transfer roller 64 away from thedistributor roller 40 without disturbing the adjustment of the controllever 104. Such disengagement of the rollers 64 and 40 is desirable whenthe machine is out of service. In this instance, the roller 64 may beretracted by swinging a hand lever 116 to the position shown in Fig. 4.It will be seen that the lever 116 is mounted on a shaft 118 whichcarries a pair of cams 120 adapted to engage follower rollers 122 or thelike on the carriages 68. When the hand lever 116 is rotated clockwiseto the position shown in Fig. 4, the high portion of each cam 120 swingsthe corresponding carriage 68 in a clockwise direction so as to retractthe roller 64 from the distributor roller 40. Movement of the lever 116in the opposite direction, to theposition shown at. Fig. 7, brings thelow portion of each earn 120 into operative relation with thecorresponding roller 122 and thereby permits the springs 76 to swing theroller 64 toward the distributor roller 40. Stop fingers 124 and 126 areprovided at the opposite ends of each cam 120 to define the range ofmovement of the lever 116.

When the roller 64 is swung away from the roller 4 by the operation ofthe disabling lever 116, the roller 64 is also separated from thefountain roller 56. This is brought about bycamming arms 130 which aremounted on pivots 132 carried by the carriages 68. Each arm 130 has afinger or shoe portion 134 which engages a fixed vertical stop orabutment 136 when the carriages 68 are swung away from the roller 40 bythe lever 116. As the carriages 68 complete their clockwise movement,the arms 130 are swung counterclockwise on the pivots 132, as shown inFig. 4. Each arm 130 has an actuating portion 138 on the opposite edgeof the arm from the shoe portion 134. The actuating portions 138 areeffective to engage and lift the bearings 69 when the arms 130 are swungclockwise. Thus, the roller 64 is moved away from the fountain roller58. The roller 64 is returned automatically against the roller 58 whenthe disabling lever 116 is operated to return the carriages 68 towardthe roller 40.

During normal operation of the repellent-feeding mechanism, thecam-operated levers 78 do not swing the carriages 68 far enough awayfrom the roller 40 to disengage the roller 64 from the fountain roller58. In other words, the cam arms 130 have sufficient lost motion to keepthem from separating the rollers 64 and 58 during normal oscillation ofthe carriages 68. The roller-separating action of the arms 130 comesinto play only when the carriages 68 are swung beyond their normal rangeby the disabling lever 116.

In the operation of the repellent system, the bottle 62 feeds repellentto the fountain 56 and maintains the level of the repellent therein. Therepellent is picked up by the rotating fountain roller 58 and is carriedto the roller 64. The pressure between the rollers 64 and 58 spreads therepellent over the surface of the roller 64 in a thin film.

The cams 86 continuously oscillate the cam follower levers 78. When thepivots 100 for the levers are adjusted as shown in Fig. 7, the rollers82 on the levers 78 engage the lugs 84 on the carriages 68 for a portionof the cycle of the earns 86. Thus, the levers 78 are effective to carrythe roller 64 away from the roller 40 for a portion of the cycle.Repellent is transferred to the roller 40 when the rollers 64 and 40 arein engagement, but not when they are separated. Thus, the amount ofrepellent which is fed to the roller 40 depends upon the portion of thecycle during which the rollers 64 and 40 are in contact.

,The oscillating movement of the roller 64 may be varied by adjustingthe position of the control lever 104 so as to rotate the shaft 102 andshift the eccentric pivots 100. Shifting the pivots moves the paths ofthe levers 78 toward and away from the carriages 68. Movement of thelevers toward the carriages 68 increases the portion of the cycle duringwhich the roller 64 is swung away from the roller 49 and therebydecreases the amount of repellent fed to the roller 40. Conversely,shifting the levers 78 away from the carirages 68 increases the amountof repellent fed to the roller 49. In one extreme position of the pivots100, shown in Fig. 5, the roller 64 is swung .away from the roller 4%during the entire cycle of the cams 86 so that there is never anycontact between the rollers 64 and 40. Fig. 7 illustrates the otherextreme position in which the levers 78 never engage the carriages 68,with the result that the roller 64 continuously engages the roller 40.

When the machine is to be shut down, or when it is desired that norepellent be fed to the master cylinder, the transfer roller 64 may beretracted from the distributor roller-40 by swinging the lever 116 tothe position shown in Fig. 4. This may be done without disturbing theposition of the control lever 104. When the lever 116 is thus moved, theearns 12% swing the carriages 68 away from the roller 40 and beyond therange of motion of the cam follower levers 78. The movement of thecarriages 68 causes the camming arms 130 to move the roller 64 away fromthe roller 58. Thus, the lever 116 provides a night latch to separatethe rollers 40, 64 and 58 when the machine is shut down overnight or forlonger periods. Returning the lever 116 to the position shown in Fig. 7again restores the repellent system to its operative condition.

It will be understood that the repellent system gives close control overthe amount of repellent fed to the master cylinder. Moreover, the amountof repellent may be adjusted over an extremely wide range. The repellentsystem may be disabled independently'of the normal adjusting means, sothat the repellent system may be re stored instantly and accurately toits operating adjustment.

Various modifications, alternative constructions and equivalents may beemployed without departing from the true spirit and scope of theinvention as exemplified in the foregoing description and defined in thefollowing claims:

I claim:

1. In a lithographic printing machine having a master cylinder forholding a lithographic printing plate, the com- 'bination comprising afirst roller arranged to convey liquid repellent to the master cylinderfor application to the printing plate, a fountain for holding a supplyof the repellent, a fountain roller rotatable in said fountain andadapted to be partly immersed in the repellent therein, a rotatabletransfer roller engaging said fountain roller, carriage means rotatablysupporting said transfer roller and mounted for swinging movement aboutan axis coinciding with the axis of said fountain roller, said transferroller thereby being swingable into and out of engagement with saidfirst roller for applying repellent thereto, a rotatable cam, means fordriving said cam at a rotary speed differing from the speed of themasten cylinder and not a multiple or sub-multiple thereof, a followerlever having a rider thereon engageable with said cam, resilient meansbiasing said follower lever to maintain said rider against said cam,said cam thereby being effective to rock said lever, said lever having aportion engageable with said carriage means for swinging the same,adjustable supporting means for said lever and including a shaft havinga pivot portion swingably supporting said lever and a' mounting portionwhich is eccentric with respect to said pivot portion, and means foradjustably rotating said shaft about the axis of said mounting portionfor shifting the axis of said lever so as to vary the time of engagementbetween said transfer roller and said first roller during each cycle ofsaid cam, the eccentricity of said pivot portion being sufiicient tovary said time of engagement from zero to continuous engagement.

2. In a printing machine having a master cylinder for holding alithographic printing master, the combination comprising a first rollerarranged to convey liquid repellent to said master cylinder forapplication to said master, a fountain for holding a supply of therepellent, a fountain roller rotatable in said fountain and adapted tobe partly immersed in the repellent therein, a transfer roller forengaging said fountain roller, swingable carn'age means rotatablysupporting said transfer roller, means supporting said carriage meansfor swinging movement about an axis substantially coinciding with theaxis of said fountain roller, said transfer roller thereby beingswingable into and out of engagement with said first roller, a leverhaving a lost motion connection to said carriage means for swinging thesame, resilient means biasing said carriage means to urge said transferroller toward said first roller, said lever being operative to swingsaid carriage means counter to said resilient means, a rotatable cam, arider on said lever engageable with said cam, means biasing said leverto maintain said rider against said cam, pivot means supporting saidlever for swinging movement, means for laterally shifting said pivotmeans to vary the time of engagement of said transfer roller with saidfirst roller between zero and continuous engagement, and a manuallyoperable cam engageable with said carriage means and operative to swingsaid transfer roller away from said first roller so as to prevent saidtransfer roller from engaging said first roller at any time.

3. In a lithographic printing machine having a master cylinder forholding a lithographic printing plate, the combination comprising afirst roller arranged to convey liquid repellent to the master cylinderfor application to the printing plate, a fountain for holding a'suppl'yof the repellent, a fountain roller rotatable in said fountain andadapted to be partly immersed in the repellent therein, a rotatabletransfer roller engaging said fountain roller, carriage means rotatablysupporting said transfer roller and mounted for swinging movement aboutan axis coinciding with the axis of said fountain roller, said transferroller thereby being swingable into and out of engagement with saidfirst roller for applying repellent thereto, a rotatable cam, means fordriving said cam at a rotary speed differing from the speed of themaster cylinder and not a multiple or sub-multiple thereof, a followerlever swingable by said cam, a lost motion connection between said leverand said carriage for swinging the same, adjustable supporting means forsaid lever and including a shaft having a pivot portion swingablysupporting said lever and a mounting portion which is eccentric withrespect to said pivot portion, and means for adjustably rotating saidshaft about the axis of said mounting portion for shifting the axis ofsaid lever so as to vary the time of engagement between said transferroller and said first roller during each cycle of saidjcam for swingingmovement about an axis substantially coinciding with the axis of saidfountain roller, said transfer roller thereby being swingable into andout of engagement with said first roller, resilient means biasing saidtransfer roller against said fountain roller, a lever having a lostmotion connection to said carriage means for swinging the same,resilient means biasing said carriagemeansto urge said transfer rollertoward said first roller, said lever being operative to swing saidcarriage means counter to said resilient means, a rotatable cam, a rideron said lever engageable with said cam, means biasing said lever tomaintain said rider against said cam, pivot means supporting said leverfor swinging movement, means for laterally shifting said pivot means tovary the time of engagement of said transfer roller with said firstroller between zero and continuous engagement, a manually operable camengageable with said carriage means and operative to swing said carriagemeans and said transfer roller away from said first roller so as toprevent said transfer roller from engaging said first roller at anytime,

operable in one direction to move said transfer roller away from saidfountain roller, and a stop engageable by said arm in the course ofmovement of said carriage means away from said first roller by saidmanually operable cam and effective to operate said arm in said onedirection to separate said transfer roller from said fountain roller.

5. In a printing machine having a master cylinder for holding alithographic printing master, the combination comprising a first rollerarranged to convey liquid repellent to said master cylinder forapplication to said master, a fountain for holding a supply of therepellent, a fountain roller rotatable in said fountain and adapted tobe partly immersed in the repellent therein, a transfer rollerengageable with said fountain roller, swingable carriage meanssupporting said transfer roller for rotation about its own axis andmovement toward and away from said fountain roller, means supportingsaid carriage means for swinging movement about an axis substantiallycoinciding with the axis of said fountain roller, said transfer rollerthereby being swingable into and out of engagement with said firstroller, resilient means biasing said transfer roller against saidfountain roller, means for cyclically rocking said carriage to move saidtransfer roller into and out of engagement with said firstroller, amanually operable cam engageable with said carriage means and operativeto swing said carriage means and said transfer roller away from saidfirst roller so as to prevent said transfer roller from engaging saidfirst roller at any time,-a swingable arm carried by said carriage meansand operable in one direction to move said transfer roller away fromsaid fountain roller, and a stop engageable by said arm in the course ofmovement of said carriage means away from said first roller by saidmanually operable cam and effective to operate said arm in said onedirection to separate said transfer roller from said fountain roller.

6. In a printing machine having a master cylinder for holding alithographic printing master, the combination comprising a first rollerarranged to convey liquid repellent to said master cylinder forapplication to said master, a fountain for holding a supply of therepellent, a fountain roller rotatable in said fountain and adapted tobe partly immersed in the repellent therein, a transfer roller aswingable arm carried by said carriage means and engageable with 'saidfountain roller, swingablexcarriage means supporting said transferroller for rotation about its own axis and movement toward and away fromsaid fountain roller, means supportingsaid carriage means for swingingmovement about an axis substantially coinciding with the axis of saidfountain roller, said transfer roller thereby being swingable into andout of engagement with said first roller, resilient means biasing saidtransfer roller against said fountain roller, means for cyclicallyrocking said carriage to move said transfer roller into and out ofengagement with said first roller, manually operable means engageablewith said carriage means and operative to swing said carriage means andsaid transfer roller away from said first roller so as to prevent saidtransfer roller from engaging said first roller at any time, a swingablearm carried by said carriage means and operable in one direction to movesaid transfer roller away from said fountain roller, and a stopengageable by said arm in the course of movement of said carriage meansaway from said first roller by said manually operable means andeffective to operate said arm in said one direction to separate saidtransfer roller from said fountain roller.

7. In a lithographic printing machine having a master cylinder forholding a lithographic printing plate, the combination comprising afirst roller arranged to convey liquid repellent to the master cylinderfor application to the printing plate, a fountain for holding a supplyof the repellent, a fountain roller rotatable'in said fountain andadapted to be partly immersed in the repellent therein, a rotatabletransfer roller engaging said fountain roller, carriage means rotatablysupporting said transfer roller and mounted for swinging movement aboutan axis coinciding with the axis of said fountain roller, said transferroller thereby being swingable into and out of engagement with saidfirst roller for applying repellent thereto, a rotatable cam, means forcontinuously rotating said cam, a follower lever having a rider thereonengageable with said cam, resilient means biasing said follower lever tomaintain said rider against said cam, said cam thereby being efiectiveto rock said lever, said lever having a portion engageable with saidcarriage fo'r swinging the same, adjustable supporting means for saidlever and including a shaft having a pivot portion swingably supportingsaid lever and a mounting portion which is eccentric with respect tosaid pivot portion, and means for adjustably rotatingsaid shaft aboutthe axis of said mounting portion for shifting the axis of said lever soas to vary the time of engagement between said transfer roller and saidfirst roller during each cycle of said cam, the eccentricity of saidpivot portion being sufficient to vary said time of engagement from zeroto continuous engagement.

8. In a lithographic printing machine having a master cylinder forholding a lithographic printing plate, the com bination comprising afirst roller arranged to convey liquid repellent to the master cylinderfor application to the printing plate, a fountain for holding a supplyof the repellent, a fountain roller rotatable in said fountain andadapted to be partly immersed in the repellent therein, a rotatabletransfer roller engaging said fountain roller, carriage means rotatablysupporting said transfer roller and mounted for swinging movement aboutan axis co'inciding with the axis of said fountain roller, said transferroller thereby being swingable into and out of engagement with saidfirst roller for applying repellent thereto, yieldable means biasingsaid carriage means in a direction to urge said transfer roller towardsaid first roller, a rotatable cam, means for continuously rotating saidcam, a follower lever having a rider thereon engageable with said cam,resilient means biasing said follower lever to maintain said rideragainst said cam, said cam thereby being effective to rock said lever,said lever having a portion engageable with said carriage means forswinging the same counter to said yieldable means and thereby movingsaid transfer roller away from said first roller, adjustable supportingmeans for said lever and including a shaft having a pivot portionswingably supporting said lever and a mounting portion which iseccentric with respect to said pivot portion, and means for adjustablyrotating said shaft about the axis of said mounting portion for shiftingthe axis of said lever so as to vary the time of engagement between saidtransfer roller and said first roller during each cycle of said cam, theeccentricity of said pivot portion being suflicient to vary said time ofengagement from zero to continuous engagement.

9. In a lithographic printing machine having a master cylinder forholding a lithographic printing plate, the combination comprising afirst roller arranged to convey liquid repellent to the master cylinderfor application to the printing plate, a fountain for holding a supplyof the repellent, a fountain roller rotatable in said fountain andadapted to be partly immersed in the repellent therein, a rotatabletransfer roller engaging said fo'untain roller, carriage means rotatablysupporting said transfer roller and mounted for swinging movement aboutan axis coinciding with the axis of said fountain roller, said transferroller thereby being swingable into and out of engagement with saidfirst roller for applying repellent thereto, yieldable means biasingsaid carriage means in a direction to urge said transfer roller towardsaid first roller, a rotatable cam, means for continuously rotating saidcam, a follower lever having a rider thereon engageable with said cam,resilient means biasing said follower lever to maintain said rideragainst said cam, said cam thereby being effective to rock said lever,said lever having a portion engageable with said carriage means forswinging the same counter to said yieldable means and thereby movingsaid transfer roller away from said first roller, adjustable supportingmeans for said lever and including a pivot swingably supporting saidlever, and means for adjustably shifting the axis of said pivot so as tovary the time of engagement between said lever and said carriage meansand thereby vary the time during which said trans- 10 fer roller isdisengaged from said first roller for each cycle of said cam.

10. In a lithographic printing machine having a master cylinder forholding a lithographic printing plate, the combination comprising atrain of rollers, one of said rollers engaging said master cylinder toapply ink and repellent to the lithographic plate thereon, means forsupplying ink to said roller train, a fountain for holding a supply ofthe repellent, a fountain roller rotatable in said fountain and adaptedto be partly immersed in the repellent therein, a transfer rollerengaging said fountain roller for receiving repellent therefrom, saidtransfer roller being mounted for swinging movement into and out ofengagement with one of the rollers of said train for supplying repellentthereto, means including a rotatable cam for effecting such swingingmovement of said transfer roller, and means for driving said cam at arotary speed generally equal to but differing slightly from the rotaryspeed of said master cylinder and not a multiple or submultiple of therotary speed of said master cylinder so that the cycles of said transferroller and said master cylinder will concur only at long intervals ofmany cycles, said last mentioned means comprising a first gear securedto and rotatable with said master cylinder, and a second gear meshingwith said first gear and secured to and rotatable with said cam, saidgears having a gear ratio generally equal to unity but diflering fromunity by a small minor fraction.

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